Actually, HD native pixel counts vary by the format.
HD formats.
HDV is 1440x1080i
DVCPRO HD is 1280x1080
HDCAM is 1440x1080 and that is just for 1080i.
There are also the 720P flavours of HD with vary in size, but mostly 1280x720 pixels.
So a 23" LCD is not really HD anymore than a 20" LCD is.
All HD formats get stretched to 1920x1080 on playback, although the resolution remains at the most, 1440x1080. The only time you may need the 23" is when you are working with Viper Filmstream HD, which comes in at the full HD resolution. I believe only 1% of the HD market can afford this level of quality.